1. Field of Invention
The present invention relates to the wireless power transmission and feedback technology, and more particularly to a wireless charging circuit and an abnormal state protection circuit thereof.
2. Related Art
Wireless charging technology is a technology for charging device by electromagnetic field without any wire. Wireless charging technology is evolved from the wireless power transmission technology to use the magnetic resonant to transmit the electrical charge from charger to device to resonate coil and capacitor between the charge and device to achieve a high efficient power transmission. The wireless charger is more safer, no exposed connections, no leakage current. Thus, a lot of problems in wired charger is prevented.
Due to the development of the wireless charging technology, Wireless Power Consortium is established because of the situation. One of accomplishments of Wireless Power Consortium is to promote Qi standard. With the standardization, wireless charging technology is more widely adopted. In Qi standard, when transmitter charges the receiver, the transmitter must decode the signal carried by the transmitted power at LC harmonic oscillator to be used for controlling the transmitting power and procedure. Therefore, the correctness of the signal transmission is pretty important.
However, when the placement of the coil of the wireless charging receiver and the position of the coil of the wireless power transmitter is not matched or there is a conductor between the coil of the wireless charging receiver and the coil of the wireless power transmitter, the wireless power receiver would continuously send a request to the wireless power transmitter to ask the wireless power transmitter to increase the output power. When the wireless power transmitter continuously operates at the resonant frequency, the current flowing through the coil of the wireless power transmitter would be continuously increased, and the temperature thereof is thus increased. Therefore, the plastic case of the wireless power transmitter may be melted. Furthermore, a fire may break out.